Lattice model of linear telechelic polymer melts. II. Influence of chain stiffness on basic thermodynamic properties

TL;DR

This paper uses lattice cluster theory to analyze how chain stiffness affects self-assembly and thermodynamic properties of linear telechelic polymer melts, revealing complex dependencies on temperature and volume fraction.

Contribution

It extends the lattice cluster theory to include chain stiffness effects, providing new insights into self-assembly behavior and thermodynamics of telechelic polymers.

Findings

Chain stiffness promotes self-assembly at high volume fraction or temperature.

Chain stiffness opposes self-assembly at low volume fraction and temperature.

Thermodynamic parameters depend strongly on chain stiffness.

Abstract

The lattice cluster theory (LCT) for semiflexible linear telechelic melts, developed in paper I, is applied to examine the influence of chain stiffness on the average degree of self-assembly and the basic thermodynamic properties of linear telechelic polymer melts. Our calculations imply that chain stiffness promotes self-assembly of linear telechelic polymer melts that assemble on cooling when either polymer volume fraction $\phi$ or temperature $T$ is high, but opposes self-assembly when both $\phi$ and $T$ are sufficiently low. This allows us to identify a boundary line in the $\phi$-$T$ plane that separates two regions of qualitatively different influence of chain stiffness on self-assembly. The enthalpy and entropy of self-assembly are usually treated as adjustable parameters in classical Flory-Huggins type theories for the equilibrium self-assembly of polymers, but they are demonstrated here to strongly depend on chain stiffness. Moreover, illustrative calculations for the dependence of the entropy density of linear telechelic polymer melts on chain stiffness demonstrate the importance of including semiflexibility within the LCT when exploring the nature of glass formation in models of linear telechelic polymer melts.